The present invention relates to a terminal control system, and in particular, to a terminal control system connected to a central processing system executing a plurality of different applications in which a plurality of applications can be executed by dynamically switching them at a terminal.
With recent developments of computer networks, there have been utilized various types of terminals, such as a terminal for an enquiry/answer system, a terminal for a file transfer operation, a terminal for emulation, and a terminal for a remote job entry processing. In the past, an online application has been fixed to a communication line in the online system, namely, different applications have been assigned to respective lines; however, the online system at present enables a plurality of online applications to be executed through a common communication line.
A terminal control system which is easy to adapt to the central processing system executing a plurality of applications and which prevents the hardware configuration from being fixed to a particular application is described in the Japanese Patent Unexamined Publication No. 58-54436. The conventional terminal control system includes a plurality of different control rule tables or protocols and a plurality of processing circuits, as shown in FIG. 5 so as to perform operations in cooperation with those for each application established in the central processing system, the protocol tables, and the processing circuits. In detail, the processing specifications for processors 53 and 54 of a central system 51 are completely different from each other. A terminal controller 52 is connected to a plurality of different terminals 68, 69, 70 . . . , in which the terminal 68 is associated with a channel or circuit including the processor 53 and the terminals 69-70 are associated with another circuit including processor 54 in data processings. Upon receiving an instruction from the processor 53, a control unit 62 refers to a table 64 to send an address of a processing program 55 to a controller processor 60, which in turn executes a processing program 66 to control the terminal 68. The processor 54 also performs a processing in the same manner stated above. In FIG. 5, reference numerals 55 and 56 indicate program memory units, reference numerals 57 and 58 indicate control units, and reference numerals 59 and 61 indicate interface portions.
In the conventional system described above, there are provided a plurality of completely different types of protocol tables and a plurality of processing circuits in which different protocols can be stored in the terminal controller 52. As can be seen from FIG. 5, however, the terminals 68 to 70 execute fixed applications, respectively. Namely, a protocol table is exclusively assigned to a terminal, which prevents a terminal from achieving a plurality of different applications.